This invention relates to improving the heat transfer to or from materials flowing in a tube. A typical application for this invention is the high-pressure polymerization of olefins in presence of free-radical-generating initiators in a tubular reactor comprising a series of discrete tubes connected in series.
When materials of high viscosity, such as partially polymerized ethylene, flow through an elongated tubular polymerization reactor, it is difficult to transfer heat to or from them. This difficulty is believed to be caused by fouling of the tube walls with layers of material. A method of improving heat transfer by imparting spiral motion to at least part of the material flowing in the tube is disclosed by U.S. application No. 093,017, filed of even date herewith and now abandoned, content of which is incorporated herein by reference. However, it is difficult to inexpensively construct means for imparting spiral motion capable of withstanding the very high forces exerted by materials flowing at high pressure differentials. Furthermore, the force of material flowing past spiral-motion-imparting devices tends to move the devices downstream relative to the tube, away from their original location.
Other difficulties encountered with spiral-flow-imparting device installed within a tube are:
(a) it is not easy to install and remove the devices, which may be necessary to obtain optimum reactor performance under different conditions;
(b) such devices are relatively expensive;
(c) such devices may become part of the tube and, therefore, need to be replaced every time the tube is replaced.
(d) such devices are adversely affected by irregularities in the tube such as eccentricity, varying diameter and lack of straightness;
(e) such devices may be subject to deformation during installation, and, therefore, are incapable of imparting spiral motion in a desired predetermined pattern.